4e0e4c00bf
SonarLint reports the latter to be better:
std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).
Signed-off-by: Rosen Penev <rosenp@gmail.com>
91 lines
2.5 KiB
C++
91 lines
2.5 KiB
C++
/*
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* Copyright 2003-2021 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef MPD_BLOCKING_NFS_CALLBACK_HXX
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#define MPD_BLOCKING_NFS_CALLBACK_HXX
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#include "Callback.hxx"
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#include "Lease.hxx"
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#include "thread/Mutex.hxx"
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#include "thread/Cond.hxx"
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#include <exception>
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class NfsConnection;
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/**
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* Utility class to implement a blocking NFS call using the libnfs
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* async API. The actual method call is deferred to the #EventLoop
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* thread, and method Run() waits for completion.
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*/
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class BlockingNfsOperation : protected NfsCallback, NfsLease {
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static constexpr std::chrono::steady_clock::duration timeout =
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std::chrono::minutes(1);
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Mutex mutex;
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Cond cond;
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bool finished;
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std::exception_ptr error;
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protected:
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NfsConnection &connection;
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public:
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BlockingNfsOperation(NfsConnection &_connection) noexcept
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:finished(false), connection(_connection) {}
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/**
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* Throws std::runtime_error on error.
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*/
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void Run();
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private:
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bool LockWaitFinished() noexcept {
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std::unique_lock<Mutex> lock(mutex);
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return cond.wait_for(lock, timeout, [this]{ return finished; });
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}
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/**
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* Mark the operation as "finished" and wake up the waiting
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* thread.
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*/
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void LockSetFinished() noexcept {
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const std::scoped_lock<Mutex> protect(mutex);
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finished = true;
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cond.notify_one();
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}
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/* virtual methods from NfsLease */
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void OnNfsConnectionReady() noexcept final;
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void OnNfsConnectionFailed(std::exception_ptr e) noexcept final;
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void OnNfsConnectionDisconnected(std::exception_ptr e) noexcept final;
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/* virtual methods from NfsCallback */
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void OnNfsCallback(unsigned status, void *data) noexcept final;
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void OnNfsError(std::exception_ptr &&e) noexcept final;
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protected:
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virtual void Start() = 0;
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virtual void HandleResult(unsigned status, void *data) noexcept = 0;
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};
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#endif
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